Fixing a flat tire for most vehicle operators has traditionally involved the use of a spare tire and the complex and dangerous process of installing it. The procedure for installing a spare tire can take up to an hour and requires that the driver pull safely to the side of the road, locate the tools, raise the vehicle using the tools, remove the damaged tire and replace it with spare wheel assembly that was being carried in the vehicle. After the spare wheel assembly is securely on, the driver lowers the vehicle and stows the damaged wheel assembly somewhere in or on the vehicle. These steps, which are used to fix a flat tire regardless of ambient temperature, time of day, and weather conditions, are usually unpleasant, challenging and sometimes dangerous to the driver. To a driver who is not experienced with tire replacement, the process can take an undue amount of time and frustration. Furthermore, this tire replacement process exposes the motorist to inherent roadside dangers.
Recently, various products have emerged to address the task of emergency tire repair and do not require the installation of a spare tire. These products include run-flat tires, liquid tire sealants, and aerosol tire sealants, to name a few. However, all of these products have drawbacks and many introduce significant challenges and danger to the average motorist.
Liquid tire sealants with unique fluid dispensing methods have been proposed. These fluid dispensing methods fall into two categories; (1) Aerosol dispensers which are comprised on compressed gas as a propellant integrated with a liquid sealant in a container and (2) Two-part liquid sealant installation kits that are comprised of a stand-alone compressed air source which can be attached to a liquid sealant container to force the liquid sealant into a tire.
Aerosol dispensers combine a chemical fluid to be dispensed with a propellant. The propellants are usually contained in a can or other type of container. A tube is attached between the can and a tire via a tire valve stem. The fluid is propelled to the tire through the tube, and into the tire through the valve stem. When the fluid reaches the punctured area of the tire, it hardens due to exposure to air. The hardened fluid forms a temporary, and in some cases a permanent, repair “patch” on the tire.
This “tire-patching” method helps eliminate some of the problems associated with replacing the punctured tire with a spare tire, such as the need to carry around a large spare wheel assembly. However, this method does not lessen the roadside danger to which the driver is exposed. In some cases, such as in the case of some commercially available aerosol tire sealants, use of the method may even pose new dangers that are not posed by the traditional spare tire method. For example, the amount of propellant in the can may not be enough to properly and safely inflate the tire to the recommended air pressure level. When an insufficient amount of propellant is used, the driver ends up operating a vehicle with a partially inflated tire. A partially-inflated tire is known to not only compromise the handling and the general maneuverability of the vehicle during vehicle operation, but also to cause premature tire failure. Of further concern is that the propellant in most aerosol sealants is highly combustible and may explode when exposed to higher temperature, or ignite when exposed to a flame.
An alternative method to tire repair is the Two-part system. The two parts include a fluid sealant and a compressed air source. The compressed air source allows proper and safe inflation of the tire, and conveniently allows tire repair without raising the car. The two-part system also leads to safe handling and control of the vehicle by allowing the tires to be inflated to the proper pressure. The Two-part systems do not expose the motorist to the above risks that are posed by the aerosol sealants.
Potential advantages of this two part system have not been fully realized for various reasons. Most Two-part systems require the air from the compressor to be forced into the sealant container through an intake. This results in the sealant being forced out of the container and into the tire through the exhaust outlet. This design tends to be potentially unreliable. For example, this type of system frequently does not dispense the sealant unless the outlet is immersed in a fluid. These type of designs will only work in certain specific orientations, compromising the reliability of the device and creating inconvenience to the user.
Another disadvantage of the two-part system is that it mixes air with fluid. In many cases, it is not desirable to mix a chemical with air, which usually contains some water vapor. Mixing air containing water vapor causes the chemical composition of the fluid to change. This change can be dramatic depending on the amounts of air, water vapor, and fluid that are involved.
Yet another disadvantage of the two-part system is the hardening of the chemical sealant after use. While being dispensed, the sealant can contact outlet surfaces and harden, forming a layer of hardened sealant on the surfaces. Since the hardened sealant is not easily removable, these hard-coated parts of the dispensing device usually require replacement. Replacement of the dispenser parts is inconvenient for the user. Moreover, the overall cost is increased and the reliability of the product is lowered because the need to incorporate replaceable parts adds to the complexity of design.
International patent WO2004/041649 (Cowan) and U.S. Pat. No. 6,789,581 (Cowan 2004) describe a container of fluid tire sealant with an intake and an exhaust. An air source supplies compressed air to the sealant container through the intake. The resulting pressure in the container pushes the sealant through an exhaust and into the punctured tire. A downside of this method is the limitation on the fluid container orientation. To effectively transfer the sealant to the tire, the exhaust has to be covered by the sealant inside the container. If the container is oriented so that the exhaust is above the sealant, only air will be pumped. Further, the air will be mixed with the fluid in this orientation. This mixing can change the fluid chemical composition without any fluid being dispensed. Also, after use, the outlet of the device becomes contaminated with hardened sealant.
International patent WO 03/041949 (Eriksen 2002) describes another variation of this pressurized container method. In this method, the compressed air does not actually enter the sealant container. It fills and pressurizes a cavity around the sealant container. The sealant container has a movable piston at one end. The pressurized cavity causes this piston to push against the sealant in the container. The resulting pressure forces the sealant through an exhaust into a punctured tire.
In WO 03/041949, a cap covering both the sealant container and the pressurized cavity serves as a valve. This cap-valve allows the system to operate simply as a compressor passing air. This cap-valve alternately allows pressurized sealant to be injected into a punctured tire. Although this method seems to be advantageous because it allows orientation-independent operation, it has its drawbacks. The combination of sealant container, cavity, and cap-valve increases complexity. This complexity increases the cost of the device and compromises system reliability. The portion of the cap-valve that comes into contact with the sealant must be replaced after use. Sealant will harden when exposed to air or moisture. This portion of the cap-valve becomes useless due to hardened sealant.
International patent WO 99/14031 (Thurner, 1999) describes a container of sealant fluid that is inside of a pressure chamber. During use, the chamber is pressurized. This pressurizing compresses the sealant container, forcing the sealant through an outlet. A disadvantage with this design is that it does not allow orientation-independent operation. Plus, this design requires incorporation of replaceable parts because of hardened sealant on the outlet parts. Moreover, since the container is compressed during use, it has to be replaced after use. Depending on the chemical composition of the fluid, it may be hazardous for the user to come into contact with the fluid. If the container does not compress completely, the sealant that remains in the container may come in contact with the user during the container-removal process.
As described above, most Two-part tire repair methods that are currently available have their disadvantages. A tire repair method that is inexpensive for the user (e.g., minimal replaceable parts required) and convenient to use (e.g., orientation-independent) is desired.